1. Field
The present disclosure generally relates to contact printing, and more specifically to a surface modification of a stamp which assist printing material transfer from stamp to substrate.
2. Background
There are two major ways to lower the cost of electronics devices—increase the packaging efficiency of the integrated circuit (IC) components of the devices, and increase cost effectiveness by using volume production processes. For such a cost-efficient mass production and even more for thin, flexible polymer electronic systems, large area patterning processes may be a choice as an economic production method and will most probably play an important part in polymer electronics manufacturing.
Such electronic devices may include a substrate, printed circuit components such as circuit traces and printed circuit elements such as resistors, and discrete components such as electrodes and other active or passive circuit elements. In many cases, the devices are printed by use of a stamp capable of transferring printing material from the stamp to a substrate in order to establish printed circuit components such as circuit traces and printed circuit elements on the substrate.
High resolution patterning methods for defining the separation between interconnects in electronic devices are important because of the flexibility of the low cost flexible substrate. As simple and efficient as it is, contact printing does nevertheless present some problems, often related to the use of the soft polymer stamp. To ensure high efficiency of transfer of printing material from the stamp, controlling the surface wettability of the stamp is therefore of major interest. FIGS. 1A-D are diagrams showing the ideal a printing procedure of contact printing. During dipping, the printing material should be easily picked up by the stamp, which has a higher surface energy relative to the printing material. While printing on the substrate, the stamp surface should have a lower surface energy relative to the printing material in order to transfer the material to the substrate. To facilitate this material transfer mechanism, control of surface wettability on the stamp surface is a key process.
Stimuli-responsive surfaces make it possible to reversibly control the wettability of the surface and has been demonstrated by various methods, including light-irradiation. Among different controlling methods on surface wettability, light-irradiation is the most effective, especially in large volume production.
U.S. Pat. No. 7,361,724 discloses surface modification by providing a self-assembling monolayer. According to this disclosure, the modified surface cannot be activated by ultraviolet source which is essential to change its properties during the printing process. U.S. Pat. No. 6,951,666 discloses the precursor to modify the surface of a stamp; however, the precursor is limited to conductive features and its application is limited. U.S. Pat. No. 7,368,163 discloses a covalent bonded surface modified on a polymer for printing. According to this disclosure, the absorbed surface modifier is not photosensitive or able to change its state under ultraviolet radiation. U.S. Pat. No. 6,884,628 discloses multifunctional polymeric surface coatings, but its application is limited to sensor devices and the described surface modification cannot be activated by ultraviolet radiation.